By means of a morphological, biochemical and functional analysis of GABA and monoamine neurons especially within limbic areas it is hoped to obtain better insights into pathogenesis of schizophrenia and depression. This goal may also be reached via an analysis of the mechanism of action of antipsychotic drugs and antidepressant drugs. The following projects are proposed. 1. By means of immunohistochemical studies on tyrosine hydroxylase and glutamic acid decarboxylase it is hoped to obtain an understanding of the morphological interactions between GABA and catecholamine (CA) neuron systems. 2. Behavioural studies will be performed to see if in animal models gabaergic compounds can potentiate the actions of neuroleptics on locomotion, rearing activity and catalepsia and also whether they could enhance the ability of neuroleptics to block the effects of apomorphine on locomotion and stereotypies. Such an analysis could help to understand whether combined treatment with neuroleptics and gabaergic drugs could be of beneficial value in the treatment of schizophrenia. 3. Various types of neuroleptic drugs will be analysed on various types of dopaminergic mechanisms in cortical regions, neostriatum and in subcortical limbic areas using studies on dopamine (DA) sensitive adenylate cyclase, using the radioligands spiroperidol and apomorphine and regional DA turnover analysis. By this approach it is hoped to clarify the existence of various types of DA receptor populations and which of them that may be mainly concerned with the antischizophrenic activity of the neuroleptics. 4. Finally, our hypothesis that blockade of certain type of 5-hydroxytryptamine (5-HT) receptors by antidepressant drugs such as amitriptyline, nortriptyline and doxepin can be of importance for their antidepressant activity, will be analysed.